There are conventionally proposed image forming apparatuses that include a post-processing unit performing so-called post-processing, such as bookbinding achieved by saddle stitching, internal folding, and the like, for a paper bundle, whose papers are used as recording media on which images are recorded by the main unit of these image forming apparatuses, such as copying machines, printers, multi-functional peripherals, and the like.
In these image forming apparatuses, the main unit and the post-processing unit are each provided with a power supply input interface (inlet) and an output interface (outlet). When, for example, only a limited number of wall outlets are provided in a room, the outlet of the main unit is connected to the inlet of the post-processing unit so that power is supplied from the main unit to the post-processing unit. If there are pluralities of post-processing units, the main unit and the plurality of processing units may be cascaded beyond a recommended number of connections.
In such a cascade connection, the current flowing in the main unit may exceed its allowable current (current rating). To address this situation, an image forming apparatus, as disclosed in Japanese unexamined patent application No. 6-121253, has a home terminal that stops power supply when the current exceeds the allowable current, and another image forming apparatus, as disclosed in Japanese unexamined patent application No. 5-38050, has a countermeasure to, for example, reduce the current for fixing a image recorded on a recording medium so that a breaker does not trip due to a consumption current exceeding the allowable current. Another image forming apparatus, as disclosed in Japanese unexamined patent application No. 2005-3886, controls the current for fixing according to the number of connected optional units and an operation mode of the image forming apparatus so that the current flowing in the main unit does not exceed the allowable current due to power supply fluctuations.
If the power supply is stopped by the home terminal described in Japanese unexamined patent application No. 6-121253 when the consumption current exceeds the allowable current, a series of operations performed by the image forming apparatus, that is, a print and bookbinding job being executed, is completely stopped, greatly reducing the productivity of printing and bookbinding.
The image forming apparatus disclosed in Japanese unexamined patent application No. 5-38050 always takes the same countermeasure for any specified printing and bookbinding jobs. Accordingly, some processing results may not satisfy user's requests. When the current for fixing is reduced, for example, the fixing temperature drops and thus the fixing time must be prolonged. However, the prolonged fixing time makes it hard to satisfy a request for high-speed printing. With the image forming apparatus disclosed in Japanese unexamined patent application No. 2005-3886, as more optional units are connected, the current flowing in the optional units is increased, making it difficult to obtain the amount of current necessary for fixing.